Hypothalamic Corticotropin-releasing Factor Research Articles

Hypothalamic CRF neurons facilitate brain reward function

Aversive stimuli activate corticotropin-releasing factor (CRF)-expressing neurons in the paraventricular nucleus of hypothalamus (PVNCRF neurons) and other brain stress systems to facilitate avoidance behaviors. Appetitive stimuli also engage the brain stress systems, but their contributions to reward-related behaviors are less well understood. Here, we show that mice work vigorously to optically activate PVNCRF neurons in an operant chamber, indicating a reinforcing nature of these neurons. The reinforcing property of these neurons is not mediated by activation of the hypothalamic-pituitary-adrenal (HPA) axis. We found that PVNCRF neurons send direct projections to the ventral tegmental area (VTA), and selective activation of these projections induced robust self-stimulation behaviors, without activation of the HPA axis. Similar to the PVNCRF cell bodies, self-stimulation of PVNCRF-VTA projection was dramatically attenuated by systemic pretreatment of CRF receptor 1 or dopamine D1 receptor (D1R) antagonist and augmented by corticosterone synthesis inhibitor metyrapone, but not altered by dopamine D2 receptor (D2R) antagonist. Furthermore, we found that activation of PVNCRF-VTA projections increased c-Fos expression in the VTA dopamine neurons and rapidly triggered dopamine release in the nucleus accumbens (NAc), and microinfusion of D1R or D2R antagonist into the NAc decreased the self-stimulation of these projections. Together, our findings reveal an unappreciated role of PVNCRF neurons and their VTA projections in driving reward-related behaviors, independent of their core neuroendocrine functions. As activation of PVNCRF neurons is the final common path for many stress systems, our study suggests a novel mechanism underlying the positive reinforcing effect of stressful stimuli.

Effect of hypoxia duration and pattern on channel Catfish (Ictalurus punctatus) neuropeptide gene expression and hematology.

Commercial aquaculture production of channel catfish (Ictalurus punctatus) occurs in shallow ponds with daily cycling of dissolved oxygen concentration ranging from supersaturation to severe hypoxia. Once daily minimum dissolved oxygen concentration falls below 3.0mg O2/L, channel catfish have a reduced appetite, leading to reduced growth rates. In other fishes, upregulation of the neuropeptides corticotropin-releasing factor (CRF) and urotensin I (UI) have been implicated as initiating the mechanism responsible for decreasing appetite once an environmental stressor is detected. Channel catfish maintained at 27°C in aquaria were subjected to varying durations and patterns of hypoxia (1.75 ± 0.07mg O2/L) to evaluate underlying physiological responses to hypoxia and determine if hypothalamic CRF and UI are responsible for hypoxia-induced anorexia in channel catfish. During a short exposure to hypoxia (12h), venous PO2 was significantly lower within 6h and was coupled with an increase of hematocrit and decrease of blood osmolality, yet all responses reversed within 12h after returning to normoxia. When this pattern of hypoxia and normoxia was repeated cyclically for 5days, these physiological responses repeated daily. Extended periods of hypoxia (5days) resulted in similar hematological responses, which did not recover to baseline values during the hypoxia exposure. This study did not find a significant change in hypothalamic transcription of CRF and UI during hypoxia challenges but did identify multiple physiological adaptive responses that work together to reduce the severity of experimentally induced hypoxia in channel catfish.

Vasopressin expressed in hypothalamic CRF neurons causes impaired water diuresis in secondary adrenal insufficiency.

Patients with secondary adrenal insufficiency can present with impaired free water excretion and hyponatremia, which is due to the enhanced secretion of vasopressin (AVP) despite increased total body water. AVP is produced in magnocellular neurons in the paraventricular nucleus of the hypothalamus (PVH) and supraoptic nucleus and in parvocellular corticotropin-releasing factor (CRF) neurons in the PVH. This study aimed to elucidate whether magnocellular AVP neurons or parvocellular CRF neurons co-expressing AVP are responsible for the pathogenesis of hyponatremia in secondary adrenal insufficiency. The number of CRF neurons expressing copeptin, an AVP gene product, was significantly higher in adrenalectomized AVP-floxed mice (AVPfl/fl) than in sham-operated controls. Adrenalectomized AVPfl/fl mice supplemented with aldosterone showed impaired water diuresis, under ad libitum access to water or after acute water loading. They became hyponatremic after acute water loading, and it was revealed under the condition that aquaporin-2 (AQP2) protein levels were increased in the kidney. Furthermore, translocation of AQP2 to the apical membrane was markedly enhanced in renal collecting duct epithelial cells. Remarkably, all these abnormalities observed in the mouse model for secondary adrenal insufficiency were ameliorated in CRF-AVP-/- mice that lacked AVP in CRF neurons. Our study demonstrates that CRF neurons in the PVH are responsible for the pathogenesis of impaired water excretion in secondary adrenal insufficiency.

The Effects of Alcohol Intoxication and Withdrawal on Hypothalamic Neurohormones and Extrahypothalamic Neurotransmitters.

The aim of the present study was to determine the effects of alcohol intoxication and withdrawal on hypothalamic neurohormones such as corticotropin-releasing factor (CRF) and arginine vasopressin (AVP), and extrahypothalamic neurotransmitters such as striatal dopamine (DA), amygdalar gamma aminobutyric acid (GABA), and hippocampal glutamate (GLU). In addition, the participation of the two CRF receptors, CRF1 and CRF2, was investigated. For this purpose, male Wistar rats were exposed to repeated intraperitoneal (ip) administration of alcohol every 12 h, for 4 days and then for 1 day of alcohol abstinence. On the fifth or sixth day, intracerebroventricular (icv) administration of selective CRF1 antagonist antalarmin or selective CRF2 antagonist astressin2B was performed. After 30 min, the expression and concentration of hypothalamic CRF and AVP, the concentration of plasma adrenocorticotropic hormone (ACTH) and corticosterone (CORT), and the release of striatal DA, amygdalar GABA, and hippocampal GLU were measured. Our results indicate that the neuroendocrine changes induced by alcohol intoxication and withdrawal are mediated by CRF1, not CRF2, except for the changes in hypothalamic AVP, which are not mediated by CRF receptors.

Intranasal administration of neuropeptide Y significantly antagonized stress-induced colonic dysmotility via central GABAA receptors in male rats.

Stress plays a major role in the pathogenesis of many diseases. Central neuropeptide Y (NPY) counteracts the biological actions of corticotropin-releasing factor (CRF) and attenuates stress responses. Intracerebroventricular (ICV) administration of NPY significantly antagonized the inhibitory effects of chronic complicated stress (CCS) on gastrointestinal (GI) dysmotility in rats. However, ICV administration is an invasive technique. The effect of intranasal administration of NPY on the hypothalamus-pituitary-adrenal (HPA) axis and GI motility in CCS conditions have not been studied, and the inhibitory mechanism of NPY on CRF through the γ-aminobutyric acid (GABA)A receptor needs to be further investigated. A CCS rat model was set up, and NPY was intranasally administered every day before the stress loading. Furthermore, ICV administration of a GABAA receptor antagonist was performed daily. Hypothalamic CRF and NPY expressions were evaluated, serum corticosterone and NPY levels were analyzed, and colonic motor functions were assessed. CCS rats showed significantly increased CRF expression and corticosterone levels, which resulted in enhanced colonic motor functions. Intranasal NPY significantly increased hypothalamic NPY mRNA expression and reduced CRF mRNA expression and plasma corticosterone levels, helping to restore colonic motor functions. However, ICV administration of the GABAA receptor antagonist significantly abolished these effects induced by NPY. In conclusion, intranasal administration of NPY upregulates the hypothalamic NPY system. NPY may, through the GABAA receptor, significantly antagonize overexpressed central CRF and attenuate HPA axis activity in CCS conditions, influencing and helping to restore colonic motor function.

(3α,5α)3-Hydroxypregnan-20-one (3α,5α-THP) Regulation of the HPA Axis in the Context of Different Stressors and Sex.

Corticotropin-releasing factor (CRF) regulates the stress response in the hypothalamus and modulates neurotransmission across the brain through CRF receptors. Acute stress increases hypothalamic CRF and the GABAergic neurosteroid (3α,5α)3-hydroxypregnan-20-one (3α,5α-THP). We previously showed that 3α,5α-THP regulation of CRF is sex and brain region dependent. In this study, we investigated 3α,5α-THP regulation of stress-induced hypothalamic CRF, CRF receptor type 1 (CRFR1), CRF binding protein (CRFBP), pro-opiomelanocortin (POMC), and glucocorticoid receptor (GR) by western blot and circulating corticosterone (CORT) by enzyme-linked immunosorbent assay (ELISA) in male and female Sprague Dawley rats. Tissue was collected after rats were injected with 3α,5α-THP (15 mg/kg, IP) or vehicle 15 min prior to 30 min of restraint stress (RS), or 10 min of forced swim stress (FSS) and 20 min recovery. The initial exposure to a stress stimulus increased circulating CORT levels in both males and females, but 3α,5α-THP attenuated the CORT response only in females after RS. 3α,5α-THP reduced GR levels in male and females, but differently between stressors. 3α,5α-THP decreased the CRF stress response after FSS in males and females, but after RS, only in female rats. 3α,5α-THP reduced the CRFR1, CRFBP, and POMC increases after RS and FSS in males, but in females only after FSS. Our results showed different stress responses following different types of stressors: 3α,5α-THP regulated the HPA axis at different levels, depending on sex.

Formation of False Context Fear Memory Is Regulated by Hypothalamic Corticotropin-Releasing Factor in Mice.

Traumatic events frequently produce false fear memories. We investigated the effect of hypothalamic corticotropin-releasing factor (CRF) knockdown (Hy-Crf-KD) or overexpression (Hy-CRF-OE) on contextual fear memory, as fear stress-released CRF and hypothalamic–pituitary–adrenal axis activation affects the memory system. Mice were placed in a chamber with an electric footshock as a conditioning stimulus (CS) in Context A, then exposed to a novel chamber without CS, as Context B, at 3 h (B-3h) or 24 h (B-24h). The freezing response in B-3h was intensified in the experimental mice, compared to control mice not exposed to CS, indicating that a false fear memory was formed at 3 h. The within-group freezing level at B-24h was higher than that at B-3h, indicating that false context fear memory was enhanced at B-24h. The difference in freezing levels between B-3h and B-24h in Hy-Crf-KD mice was larger than that of controls. In Hy-CRF-OE mice, the freezing level at B-3h was higher than that of control and Hy-Crf-KD mice, while the freezing level in B-24h was similar to that in B-3h. Locomotor activity before CS and freezing level during CS were similar among the groups. Therefore, we hypothesized that Hy-Crf-KD potentiates the induction of false context fear memory, while Hy-CRF-OE enhances the onset of false fear memory formation.

Oxytocin as an adolescent treatment for methamphetamine addiction after early life stress in male and female rats

Early life stress (ELS) is associated with perturbed neural development and augmented vulnerability to mental health disorders, including addiction. How ELS changes the brain to increase addiction risk is poorly understood, and there are no therapies which target this ELS-induced vulnerability. ELS disrupts the oxytocin system, which can modulate addiction susceptibility, suggesting that targeting the oxytocin system may be therapeutic in this ELS-addiction comorbidity. Therefore, we determined whether adolescent oxytocin treatment after ELS could: (1) reduce vulnerability to anxiety, social deficits, and methamphetamine-taking and reinstatement; and (2) restore hypothalamic oxytocin and corticotropin-releasing factor expressing neurons and peripheral oxytocin and corticosterone levels. Long Evans pups underwent maternal separation (MS) for either 15 min or 360 min on postnatal days (PND) 1–21. During adolescence (PNDs 28–42), rats received a daily injection of either oxytocin or saline. In Experiment 1, adult rats were assessed using the elevated plus-maze, social interaction procedure, and methamphetamine self-administration procedure, including extinction, and cue-, methamphetamine- and yohimbine-induced reinstatement. In Experiment 2, plasma for enzyme immunoassays and brain tissue for immunofluorescence were collected from adult rats after acute stress exposure. Adolescent oxytocin treatment ameliorated ELS-induced anxiety and reduced methamphetamine- and yohimbine-induced reinstatement in both sexes, and suppressed methamphetamine intake and facilitated extinction in males only. Additionally, adolescent oxytocin treatment after ELS restored oxytocin-immunoreactive cells and stress-induced oxytocin levels in males, and attenuated stress-induced corticosterone levels in both sexes. Adolescent oxytocin treatment reverses some of the ELS effects on later-life psychopathology and vulnerability to addiction.

Brain-wide perception of the emotional valence of light is regulated by distinct hypothalamic neurons

Salient sensory stimuli are perceived by the brain, which guides both the timing and outcome of behaviors in a context-dependent manner. Light is such a stimulus, which is used in treating mood disorders often associated with a dysregulated hypothalamic-pituitary-adrenal stress axis. Relationships between the emotional valence of light and the hypothalamus, and how they interact to exert brain-wide impacts remain unclear. Employing larval zebrafish with analogous hypothalamic systems to mammals, we show in free-swimming animals that hypothalamic corticotropin releasing factor (CRFHy) neurons promote dark avoidance, and such role is not shared by other hypothalamic peptidergic neurons. Single-neuron projection analyses uncover processes extended by individual CRFHy neurons to multiple targets including sensorimotor and decision-making areas. In vivo calcium imaging uncovers a complex and heterogeneous response of individual CRFHy neurons to the light or dark stimulus, with a reduced overall sum of CRF neuronal activity in the presence of light. Brain-wide calcium imaging under alternating light/dark stimuli further identifies distinct and distributed photic response neuronal types. CRFHy neuronal ablation increases an overall representation of light in the brain and broadly enhances the functional connectivity associated with an exploratory brain state. These findings delineate brain-wide photic perception, uncover a previously unknown role of CRFHy neurons in regulating the perception and emotional valence of light, and suggest that light therapy may alleviate mood disorders through reducing an overall sum of CRF neuronal activity.

Effect of rapid eye movement sleep deprivation during pregnancy on glucocorticoid receptor regulation of HPA axis function in female offspring

Poor maternal sleep quality during the different phases of pregnancy acts as a prenatal stress and is critical for fetal development. Despite the potential adverse effects of maternal stress on the behavior and physiology of the offspring, the mechanisms remain poorly understood. The present study investigates the effects of maternal sleep deprivation (SD) at different stages of pregnancy on the hypothalamic–pituitary–adrenal (HPA) axis in female offspring. The pregnant rats were subjected to sleep deprivation of 12 h per day at different stages; early (ESD), mid (MSD), and late (LSD) stages, on pregnancy days 1–7, 8–14, and 14–20, respectively. At postnatal day 60, levels of corticosterone (CORT), hypothalamic corticotropin-releasing factor receptor 1 (CRF-R1), and hippocampal glucocorticoid receptors (GR) were evaluated in the offspring. Although the hypothalamic CRF-R1 level was increased in the offspring of SD dams, immunohistochemical staining showed reduced immunoreactivity of GR in ESD and LSD offspring hippocampal area. Altogether, the data suggests that a critical period for adverse effects of SD on the HPA axis in female offspring of Wistar rats may be during early and late pregnancy.

Blast-Induced Mild Traumatic Brain Injury Alterations of Corticotropin-Releasing Factor Neuronal Activity in the Mouse Hypothalamic Paraventricular Nucleus.

Blast-induced mild traumatic brain injury (mbTBI) is the most common cause of TBI in US service members and veterans. Those exposed to TBI are at greater risk of developing neuropsychiatric disorders such as posttraumatic stress disorder, anxiety and depressive disorders, and substance use disorders following TBI. Previously, we have demonstrated that mbTBI increases anxiety-like behaviors in mice and dysregulates stress at the level of corticotropin-releasing factor (CRF) neurons in the paraventricular nucleus (PVN). To expand on how mTBI may dysregulate the stress axis centrally, here PVN CRF neuronal activity was evaluated using whole cell-patch clamp recordings in hypothalamic slices from sham and mbTBI adult male CRF:tdTomato mice 7 days post-injury. We found that mbTBI generally did not affect the neuronal excitability and intrinsic membrane properties of PVN CRF neurons; this injury selectively increased the frequency of spontaneous neuronal firing of PVN CRF neurons localized to the dorsal PVN (dPVN) but not ventral PVN (vPVN). Consistently, mbTBI-induced dPVN CRF hyperactivity was associated with pre- and post-synaptic depression of spontaneous GABAergic transmission onto dPVN CRF neurons suggesting that mbTBI-induced GABAergic synaptic dysfunction may underlie dPVN CRF neuronal hyperactivity and increases in dPVN CRF signaling. The present results provide the first evidence for mbTBI-induced alterations in PVN CRF neuronal activity and GABAergic synaptic function that could mediate hypothalamic CRF dysregulation following mbTBI contributing to stress psychopathology associated with blast injury.

Single-Cell Transcriptional Changes in Hypothalamic Corticotropin-Releasing Factor–Expressing Neurons After Early-Life Adversity Inform Enduring Alterations in Vulnerabilities to Stress

BackgroundMental health and vulnerabilities to neuropsychiatric disorders involve the interplay of genes and environment, particularly during sensitive developmental periods. Early-life adversity (ELA) and stress promote vulnerabilities to stress-related affective disorders, yet it is unknown how transient ELA dictates lifelong neuroendocrine and behavioral reactions to stress. The population of hypothalamic corticotropin-releasing factor (CRF)–expressing neurons that regulate stress responses is a promising candidate to mediate the long-lasting influences of ELA on stress-related behavioral and hormonal responses via enduring transcriptional and epigenetic mechanisms. MethodsCapitalizing on a well-characterized model of ELA, we examined ELA-induced changes in gene expression profiles of CRF-expressing neurons in the hypothalamic paraventricular nucleus of developing male mice. We used single-cell RNA sequencing on isolated CRF-expressing neurons. We determined the enduring functional consequences of transcriptional changes on stress reactivity in adult ELA mice, including hormonal responses to acute stress, adrenal weights as a measure of chronic stress, and behaviors in the looming shadow threat task. ResultsSingle-cell transcriptomics identified distinct and novel CRF-expressing neuronal populations, characterized by both their gene expression repertoire and their neurotransmitter profiles. ELA-provoked expression changes were selective to specific subpopulations and affected genes involved in neuronal differentiation, synapse formation, energy metabolism, and cellular responses to stress and injury. Importantly, these expression changes were impactful, apparent from adrenal hypertrophy and augmented behavioral responses to stress in adulthood. ConclusionsWe uncover a novel repertoire of stress-regulating CRF cell types differentially affected by ELA and resulting in augmented stress vulnerability, with relevance to the origins of stress-related affective disorders.

Activation of CRF1 receptors expressed in brainstem autonomic nuclei stimulates colonic enteric neurons and secreto-motor function in male rats.

Hypothalamic corticotropin-releasing factor (CRF) receptor 1 (CRF1 ) plays a role in acute stress-related stimulation of colonic motor function. Less is known on CRF1 signaling in the brainstem. We investigate CRF1 expression in the brainstem and the colonic response to 4th ventricle (4V) injection of CRF and urocortin (Ucn) 2 (3 µg/rat) in chronically cannulated male rats. Transcripts of CRF1 wild-type 1a and splice variants 1c, 1e, 1f, 1o along with three novel variants 1a-2 (desK-110 in exon 5), 1p (-exon 7), and 1q (exon 5 extension) were identified in the pons and medulla. The area postrema, nucleus tractus solitarius, dorsal motor nucleus of the vagus, locus coeruleus, and Barrington's nucleus isolated by laser capture microdissection expressed 1a, 1a-2, and 1p but not 1q. Compared to 4V vehicle, 4V CRF induced fecal pellet output (FPO) and diarrhea that were blocked by the CRF antagonist, astressin-B. CRF2 agonist, Ucn2 had no effect on basal or CRF-induced FPO. CRF actions were correlated with the induction of c-Fos immunoreactivity in myenteric neurons of the proximal and distal colon (pC, dC) and submucosal neurons of dC. c-Fos immunoreactivity occurred in 39% and 37% of myenteric cholinergic and 7% and 58% of nitrergic neurons in the pC and dC, respectively. CRF1a and its splice variants are expressed in brainstem nuclei, and activation of CRF1 signaling at the level of the brainstem stimulates colonic secretory-motor function through activation of colonic enteric neurons.

Effects of stocking density on the performance, tibia mineralization, and the expression of hypothalamic appetite genes in broiler chickens

Abstract The current study investigated the effects of stocking density (SD) on the performance, tibia mineralization, and the hypothalamic appetite genes expression in broilers. A total of 2,800 1-d-old male broilers (Cobb 500) were distributed in a completely randomized design to 1 of 5 SD treatments with 8 replicate cages for each treatment. The SD treatments were 12.5, 15.0, 17.5, 20.0, and 22.5 birds/m2, corresponding to 50, 60, 70, 80, and 90 birds per cage (4 m2/cage), respectively. The concentration of tibia phosphorus was determined by the ammonium metavanadate colorimetric method and the mRNA abundance in different tissues was measured by the real-time quantitative PCR method. The data were analyzed by the one-way and/or two-way analysis of variance and polynomial contrasts were used to determine the effect of increasing SD. Feed intake linearly decreased (P < 0.05) with increasing SD during d 1-42 production period. On d 42, body weight and tibia breaking strength were significantly lower in the groups of 17.5, 20.0 and 22.5 birds/m2 than in the groups of 12.5 and 15 birds/m2 (P < 0.01). Concentrations of ash and phosphorus in the tibia of broilers linearly decreased (P < 0.03) with increasing SD on d 42. The SD of 22.5 birds/m2 decreased the mRNA abundance of neuropeptide Y (NPY), NPY-receptor (NPYR) 1, and NPYR2 (P < 0.05), while it increased melanocortin receptor 4 mRNA abundance (P = 0.012) in the hypothalamus of broilers as compared with the SD of 12.5 birds/m2 on d 21 and 42. The mRNA abundance of hypothalamic cocaine and amphetamine-regulated transcript (CART), corticotrophin-releasing factor (CRF), and CRF-receptor 1 (CRFR1) were higher (P < 0.05) in the group of 22.5 birds/m2 than in the group of 12.5 birds/m2 on d 21. We concluded that increasing stocking density beyond 15 birds/m2 (corresponding to the 45 kg/m2 at 42 days of age) suppressed final BW and bone mineralization of broilers raised in multitier cage system. Hypothalamic NPY and CRF signaling might be involved in the anorexigenic effect of HSD.

Sexual dimorphism in maternally separated rats: effects of repeated homotypic stress on gastrointestinal motor functions.

Experiencing stressful events during early life has been considered as a risk factor for development of functional gastrointestinal disorders in adulthood. This study aimed to investigate the sex-related differences in stress-induced gastrointestinal (GI) dysmotility in rats exposed to neonatal maternal separation (MS). Newborn pups were removed from mothers for 180min from postnatal day-1 to day-14. Experiments were performed in male and female offsprings at adulthood. Elevated plus maze (EPM) test was used to assess MS-induced anxiety-like behaviors. Ninety minute of restraint stress was applied for once or 5 consecutive days for acute stress (AS) or repeated homotypic stress (RHS), respectively. Measurement of fecal output (FO) and gastric emptying (GE), and hypothalamic microdialysis were performed. Both in males and females, MS produced anxiety-like behaviors. AS delayed GE and increased FO in all groups. In RHS-loaded MS females, AS-induced alterations in GE and FO were restored, however, no adaptation was observed in male counterparts. Regardless of sex and neonatal stress experience, AS significantly increased corticotropin-releasing factor (CRF) release from paraventricular nucleus of hypothalamus, whereas females were found more susceptible than males. Following RHS, AS-induced elevations in CRF release were attenuated only in MS females, but not in males. Both females and males seem to be prone to AS-induced alterations in hypothalamic CRF system and in GI motor functions. Neonatal MS disturbs chronic stress coping mechanisms in males. Conversely, females are likely to circumvent the deleterious effects of neonatal MS on GI functions through developing a habituation to prolonged stressed conditions.

Chronic oxytocin-driven alternative splicing of Crfr2α induces anxiety

The neuropeptide oxytocin (OXT) has generated considerable interest as potential treatment for psychiatric disorders, including anxiety and autism spectrum disorders. However, the behavioral and molecular consequences associated with chronic OXT treatment and chronic receptor (OXTR) activation have scarcely been studied, despite the potential therapeutic long-term use of intranasal OXT. Here, we reveal that chronic OXT treatment over two weeks increased anxiety-like behavior in rats, with higher sensitivity in females, contrasting the well-known anxiolytic effect of acute OXT. The increase in anxiety was transient and waned 5 days after the infusion has ended. The behavioral effects of chronic OXT were paralleled by activation of an intracellular signaling pathway, which ultimately led to alternative splicing of hypothalamic corticotropin-releasing factor receptor 2α (Crfr2α), an important modulator of anxiety. In detail, chronic OXT shifted the splicing ratio from the anxiolytic membrane-bound (mCRFR2α) form of CRFR2α towards the soluble CRFR2α (sCRFR2α) form. Experimental induction of alternative splicing mimicked the anxiogenic effects of chronic OXT, while sCRFR2α-knock down reduced anxiety-related behavior of male rats. Furthermore, chronic OXT treatment triggered the release of sCRFR2α into the cerebrospinal fluid with sCRFR2α levels positively correlating with anxiety-like behavior. In summary, we revealed that the shifted splicing ratio towards expression of the anxiogenic sCRFR2α underlies the adverse effects of chronic OXT treatment on anxiety.

(3α,5α)3-hydroxypregnan-20-one (3α,5α-THP) regulation of hypothalamic and extrahypothalamic corticotropin releasing factor (CRF): Sexual dimorphism and brain region specificity in Sprague Dawley rats

CRF is the main activator of the hypothalamic-pituitary-adrenal (HPA) axis in response to stress. CRF neurons are found mainly in the hypothalamus, but CRF positive cells and CRF1 receptors are also found in extrahypothalamic structures, including amygdala (CeA), hippocampus, NAc and VTA. CRF release in the hypothalamus is regulated by inhibitory GABAergic interneurons and extrahypothalamic glutamatergic inputs, and disruption of this balance is found in stress-related disorders and addiction. (3α,5α)3-hydroxypregnan-20-one (3α,5α-THP), the most potent positive modulator of GABAA receptors, attenuates the stress response reducing hypothalamic CRF mRNA expression and ACTH and corticosterone serum levels. In this study, we explored 3α,5α-THP regulation of hypothalamic and extrahypothalamic CRF mRNA and peptide expression, in male and female Sprague Dawley rats, following vehicle or 3α,5α-THP administration (15 mg/kg). In the hypothalamus, we found sex differences in CRF mRNA expression (females +74%, p < 0.01) and CRF peptide levels (females −71%, p < 0.001). 3α,5α-THP administration reduced hypothalamic CRF mRNA expression only in males (−50%, p < 0.05) and did not alter CRF peptide expression in either sex. In hippocampus and CeA, 3α,5α-THP administration reduced CRF peptide concentrations only in the male (hippocampus −29%, p < 0.05; CeA −62%, p < 0.01). In contrast, 3α,5α-THP injection increased CRF peptide concentration in the VTA of both males (+32%, p < 0.01) and females (+26%, p < 0.01). The results show sex and region-specific regulation of CRF signals and the response to 3α,5α-THP administration. This data may be key to successful development of therapeutic approaches for stress-related disorders and addiction.

Exposure to eagle owl feces induces anti-predator behavior, physiology, and hypothalamic gene responses in a subterranean rodent, the plateau zokor (Eospalax baileyi)

Predator odors are natural stressors that induce anti-predator defensive responses, which have developed under evolutionary pressures to maximize the fitness of an individual to avoid dangerous confrontations. In this study, we analyzed the defensive responses of a subterranean rodent species, the plateau zokor (Eospalax baileyi), to predation threat, and examined the trade-offs between defensive responses and foraging. Plateau zokors were exposed to 1, 3, and 6 g of eagle owl (Bubo bubo) feces, and the anti-predator behavioral, hormonal, and hypothalamic corticotropin-releasing factor and c-fos mRNA expression responses were analyzed and compared with the control (distilled water). Exposure of the animals to owl feces led to significant reductions in both duration of feeding and amount of food consumed, while some defensive behavioral responses (e.g., freezing and rearing) were more significant in the exposed animals than in the control. Serum levels of adrenocorticotropic hormone and corticosterone in plateau zokors exposed to owl feces were significantly higher compared with the control. The hypothalamic corticotropin-releasing factor and c-fos mRNA expression levels of plateau zokors exposed to 1, 3, and 6 g owl feces increased significantly, concomitant with the amount of eagle owl feces presented. Owl feces induced various behavioral, hormonal, and hypothalamic gene expression changes in plateau zokors exposed to them. Some behavioral and gene expression (but not hormonal) responses appeared to be threshold dependent. Predator odors supersede other signals and can provide comprehensive information to prey during life-threatening events. The plateau zokor is a typical subterranean rodent living in dark and enclosed subterranean habitats. Owing to this special habitat, zokors may be able to recognize ground predator odors and respond defensively. We investigated changes in behavior, hormones, and the hypothalamic corticotropin-releasing factor and c-fos mRNA expression levels of the plateau zokor when exposed to different amounts of eagle owl feces. We believe that our study makes a significant contribution to the literature because our results support the predation risk allocation hypothesis, showing that eagle owl feces inhibit foraging and induce various anti-predatory behavioral and neuroendocrine responses in plateau zokors.

Gastrodiae Rhizoma Water Extract Ameliorates Hypothalamic-Pituitary-Adrenal Axis Hyperactivity and Inflammation Induced by Chronic Unpredictable Mild Stress in Rats.

Gastrodiae Rhizoma is a highly valuable traditional herbal medicine commonly used to treat neurological disorders. The present study is designed to determine the antidepressant-like effect of the Gastrodiae Rhizoma water extract (GRWE) on a depression model and the potential mechanisms. The chronic unpredictable mild stress (CUMS) rat model was used to induce depression. The sucrose preference test, open field test, forced swimming test, and tail suspension test were performed to assess the depressive-like behaviors, respectively. Hypothalamic–pituitary–adrenal (HPA) function was measured via plasma corticosterone (CORT), adrenocorticotrophic hormone (ACTH), hypothalamic corticotropin-releasing factor (CRF), and glucocorticoid receptor (GR) concentrations. Plasma concentrations of proinflammatory cytokines including interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) were also evaluated. The results showed that GRWE significantly attenuates the behavioral abnormalities in CUMS rats, as shown by elevated sucrose consumption, raised locomotor activity, and reduced immobility duration. Moreover, GRWE treatment reduced CORT, ACTH, CRF, and GR levels and decreased the plasma IL-1β, IL-6, and TNF-α concentrations. These findings indicate that GRWE improves depressive behaviors in a chronic stress model of rats; its effect may be ascribed to the modulation of the HPA axis activity and inflammatory response.

N-3 PUFA improved pup separation-induced postpartum depression via serotonergic pathway regulated by miRNA

Stress and ovarian hormone fluctuation are risk factors for postpartum depression (PPD). Previous studies suggested antidepressant-like effects of n-3 polyunsaturated fatty acids (PUFA), but their effect on dam animal with additional stress were not clear. The purpose of the present study was to investigate the hypothesis that n-3 PUFA improved PPD through the serotonergic and glutamatergic pathways by modulating miRNA. Rats were fed n-3 PUFA or control diet from gestation, with pup separation (PS) on postpartum days 2–14 and non-PS controls. N-3 PUFA reversed PS-induced depressive behaviors, including increased immobility, latencies to contact first pup and retrieve all pups, and decreased sucrose preference. N-3 PUFA also modulated the hypothalamic–pituitary–adrenal (HPA) axis by decreasing circulating levels of adrenocorticotropic hormone and corticosterone and expression of hypothalamic corticotrophin releasing factor and hippocampal miRNA-218 but increasing the hippocampal expression of glucocorticoid receptor. N-3 PUFA inhibited neuroinflammation by decreasing circulating levels of prostaglandin E2 and hippocampal expression of tumor necrosis factor-α, interleukin-6, and miRNA-155. In addition, n-3 PUFA up-regulated the serotonergic pathway by increasing circulating levels of serotonin and hippocampal expression of serotonin-1A receptor, cAMP response element binding protein (CREB), pCREB, brain-derived neurotrophic factor, and miRNA-182 but did not affect the glutamatergic pathway according to the hippocampal expression of N-methyl-D-aspartate receptor-2B. The present study suggested that n-3 PUFA improved PPD through the serotonergic pathway by modifying the HPA axis, neuroinflammation, and related miRNAs.